Description of the treatment process
The ABR is at the top of the hill and is operated through gravitational force. It consists of settler- thickening tank and 4 baffled reactors. Besides, there is a provision of planted filtration unit using different sizes gravel and sand. The separated liquid part (leachate) of raw FS pre-treated on drying beds further undergone with phytoremediation filtration chamber and followed by a polishing pond. The effluent discharged into the environment within the Bangladesh effluent discharge standards. Canna indica is the perennial plant used in the filtration unit to aid further leachate treatment. Inside the settler tank, the solid settles down in the ABR and the liquid overflows through a PVC pipe. The liquid goes to the filtration system and after filtering that water, effluent water comes out of the filtration unit and finally in the polishing pond. There is a drying bed for drying purpose of separated solids. These consist of different layers of gravel-sand filter media of different thickness and gavel size. The benefits of these beds include no requirement and use of power. The drying process is enhanced by evaporation and solid-liquid separation by gravity percolation of leachate. There is a scope to use dried sludge as soil conditioner.
Description of the emergency context
Living area of community (name and localization of camp/city/village, access): Kutupalong Camp Area in different locations Local and international WaSH institutions (management committees, NGOs, WaSH governmental agencies, private sector) with WaSH active role in the community and specific partnerships: NGO Forum and other development organization such as BRAC, ACF, PCCR, IFRC, Friendship etc. Main waterborne diseases: Cholera, Diarrhea, Dysentery, Typhoid etc.
The terrain is a hilly region which has ups and downs but NGOF considered the low lands beneath the hill for the construction of fecal sludge treatment/disposal site. It is protected in such a way that people can’t see the sludge and it restricts the spreading of virus. Raw sludge is untreated non-stabilized sludge, which can be taken from wastewater treatment plants. The details FS characterization of raw sludge was not undertaken during design. The sludge comes from pit latrines and septic tanks. Water is used for anal cleansing. NGO Forum does the desludging through convenes pipe with the help of pumping and maintains proper health safety such as: Mask, Hand Gloves, Gum Boot, Apron, Rake, Convenes Pipe, Octane running Pump, Generator, submersible pump. Besides this, NGO Forum also desludges through transfer stations with the capacity of ten (10) thousand-liter plastic tank using gravitational force. The design was developed based on the secondary information and data. Considered treatment performance of ABRs is in the range of 65% to 90% COD (Chemical Oxygen Demand) removal, corresponding to about 70% to 95% of BOD (Biological Oxygen Demand) removal. The majority of the settleable solids are removed in the sedimentation chamber at the beginning of the ABR, which typically represents 50 % of the total volume of TSS. The special design also allows for an enhanced treatment of non-settleable solids and a Total Suspended Solids (TSS) removal of up to 90% can be achieved. ABRs are a combination of the principles of septic tanks, moving bed reactors and up-flow anaerobic sludge blanket reactors. The majority of settleable solids are removed at the settler and thickening tank in front of the ABR. The inflow is up to 35 m3 per day in this system. Critical design parameters include a hydraulic retention time (HRT) between 48 to 72 hours, up-flow velocity of the wastewater below 0.6 m/h and the number of up-flow 4 chambers. Vertical baffles in the tank force the pre-settled wastewater to flow under and over the baffles guaranteeing contact between wastewater and faecal sludge and allowing an enhanced anaerobic digestion of suspended and dissolved solids. The connection between the chambers are designed either with vertical pipes with baffles. Accessibility to all chambers (through access ports) is necessary for maintenance. The tank is with cover to allow for control of the ABR system. In addition, provided a biological filtration for treatment of effluent water comes from reactor which enable bacterial colonies to propagate and break down wastes.
It is a safely managed FSM system with biological treatment and environment friendly. There is scope to create the opportunity from this where community people are economically benefited.
If we construct small sewerage borehole and increase secondary transfer station, safety tank then the cost will be reduced. By constructing small sewerage borehole or transfer station, we can reduce contacts between staff and sludge. Ensuring community engagement and engaging skilled volunteer’s can guarantee the sustainability of the plant. Specific challenges: • emptying frequency too high as a result it is difficult to maintain retention periods. • leakage of convenes pipe • quality of effluent water • space in the camps is limited due to the number of people and topography • landslides in the rainy season